26 BULLETIN" 327, U. S. DEPARTMENT OF AGRICULTURE. 



crowding and upright position of the leaves on the upper sides of the 

 branches is very characteristic. Leaves of the " leader " or topmost 

 central stem (PL XII, a) are sharply pointed and scattered. 



Mature cones of the alpine fir are from 2| to about 4 inches in 

 length by about li to 1J inches in diameter (PL XI) ; after the cone 

 scales, become loosened by drying out, the cones are considerably 

 larger in diameter. Ripe cones are deep purple at first, gradually 

 becoming lighter by the time the scales fall. The cone scales bear 

 bracts (PL XI, a), which are abruptly rounded or contracted at the 

 free end to a slender central point. The ivory -brown seeds (PL 

 XI, b ) have large, shiny, purplish, or violet-tinged wings. The seed- 

 leaves, one-third to one-half an inch long, are usually 4 in number. 



Alpine fir wood is lighter in weight than that of any other Rocky 

 Mountain fir, a cubic foot of dry wood weighing about 21.66 pounds. 

 It is narrow-ringed, soft, and from pale straw-color to light yellowish 

 brown. As a rule, the wood is fairly straight-grained and splits and 

 works easily, but it rots rapidly in contact with earth. However, 

 the fire-killed, deeply season-checked shafts of this tree, so frequent 

 where forest fires have swept the ground, may remain sound above 

 ground for many years. Dead timber is locally much used for fuel, 

 house logs, and corral poles. Occasionally green timber is sawed into 

 rough lumber for local use. Little clear lumber is, however, obtain- 

 able even from large trees, because during the greater part of life the 

 lower trunk branches are retained down to the ground. 



OCCURRENCE AND HABITS. 



Alpine fir always grows in cool, moist, and, in part, subalpine 

 situations. It occurs commonly on all slopes at timber line, and, at 

 the lower limits of vertical range, in protected valleys, at the heads 

 of streams, and about mountain lakes and moist meadows (Map 

 No. 6). At the North its lowest vertical range is about 3,500 feet, 

 though at the South it may reach an elevation of 10,500 feet. Alpine 

 fir has a narrow range in altitude at the North, where the timber line 

 is relatively low, and at and near which the moisture conditions neces- 

 sary for its growth are present. Likewise at the South, the vertical 

 range of this fir is narrow, because here the timber line, with the 

 accompanying moisture conditions, occurs only at higher elevations. 

 The best growth occurs on north slopes in fairly deep, loose, moist 

 soil, while much smaller trees are found in the poorest and driest thin 

 soils. It grows also in wet situations, but it does not thrive on heavy, 

 clayey soils. Its main occurrence is^ limited by requirement of soil 

 moisture to elevations where snowfall is heavy. In general, how- 



